Mekong Plaza, the west Mesa complex that’s home to Mekong Supermarket and 30 Asian-owned restaurants and shops, has broken ground to add more than 35,000 square feet to its existing 100,000 on the southwest corner of Main and Dobson. The $10 million construction project is expected to take a year, but Mekong’s owners say more than 60 percent of the new space already has been leased.